Horse raced around middle of croft (4)
I believe the answer is:
roan
'horse' is the definition.
(roan is a kind of horse)
'raced around middle of croft' is the wordplay.
'raced' becomes 'ran' ('run' can be a synonym of 'race').
'around' is an insertion indicator.
'middle of' indicates the central letters.
The middle letter of 'croft' is 'o'.
'ran' going around 'o' is 'ROAN'.
(Other definitions for roan that I've seen before include "Reddish-coloured horse" , "Horse with a brownish coat sprinkled with grey" , "Bay spotted" , "Horse with brownish coat speckled with white" , "Red-coloured horse" .)